Final answer:
True, tonicity determines the movement of water across a membrane due to osmosis, influenced by the osmolarity of a solution. It dictates whether a cell will swell, shrink, or remain the same size, which is vital for cellular functions and survival.
Step-by-step explanation:
True, tonicity describes the effect of a solution on the movement of water. Osmolarity determines the tonicity of a solution, with tonicity influencing how water moves across a semipermeable membrane in response to solute concentration gradients; this process is known as osmosis. When a solution has lower osmolarity (hypotonic), it has a higher concentration of water compared to the solutes within, causing water to move into the cell, potentially causing it to swell or even burst (lyse).
Conversely, when a solution has higher osmolarity (hypertonic), it has fewer water molecules relative to solutes, leading to water moving out of the cell and causing the cell to shrink. A solution is isotonic when its solute concentration is equal to that within the cell, resulting in no net water movement and no change in cell volume. Maintaining tonicity is vital for cell survival, as extreme hypo- or hypertonic conditions can compromise or even destroy cellular functions.